In an irregular decoder of a regular code, variables with better quality metrics have a greater chance of receiving message updates in early decoding stages. In later stages, variables with worse quality metrics have a greater chance of receiving updates.
During low-density parity-check decoding iterations, columns are sorted to determine which columns to update. Sorting of a long vector involves long latency and extra sorting logic in circuit.
Consequently, it would be advantageous if an apparatus existed that is suitable for selecting update candidates in a low-density parity-check decoding process without sorting all of the message columns.